Art: Is there anything left to say about the Mona Lisa

Probably harder. Leonardos don’t travel. You have to go to them, for similar reasons to the ones that encouraged Muhammad to approach the mountain. It’s a scale thing.

With no prospect of anyone anywhere ever being able to put together a substantial grouping of Leonardo’s few remaining paintings, it’s been fun this year savouring the obvious frustration of the international media community as it struggled to find ways to celebrate the 500th birthday of the Mona Lisa. Nobody has anything new to say about her, of course. It’s all been said before. Nobody can get their hands on the painting. But the Mona Lisa is the most famous work of art on the planet, and Leonardo is the world’s most recognisable genius, so the anniversary-chasers had to attempt something. Thus, on television, the brooding Shakespearian Mark Rylance pretended to be Leonardo in the BBC’s recent three-part attempt to create something out of nothing. Full marks for effort. None for insight. Much more productively, at Buckingham Palace, the Queen has allowed a selection of her wondrous cache of Leonardo drawings to go pertinently on show. Thank you, Ma’am. This is more like it.

The royal Leonardo drawings are among this country’s greatest art treasures. But because they have spent most of their history secreted about the drawers of Windsor Castle, and because they are “only” drawings, they have somehow managed to maintain an absurdly low artistic profile for more than 300 years, since Charles II acquired them. Indeed, the entire royal collection has pulled off the difficult and regrettable trick of hiding something huge and marvellous under our noses in the centre of London. The only people I see at the Queen’s Gallery are merchandise-hunters from abroad, taking it in as part of the tatty Buckingham Palace experience. The great monarchical art holdings succeed in playing a thoroughly negligible role in the nation’s cultural life.

Which is a shame, because the Leonardo drawings probably constitute the world’s most wide-scale and tangible display of his talents. Early in the show, we catch up with him on a dissecting table as he dashes off a tiny profile of a skull from life and, to highlight the skull’s regular proportions, inks a square around it. The image is about the size and proportion of a postage stamp. But when you lean in to see it clearly, it packs the observational punch of a cinema screen.

How did he cut the points of his goose quill fine enough to record all this detail? How can such a stern piece of anatomy be so achingly beautiful? The Queen’s cache of Leonardo drawings is huge: some 600 sheets. The fraction on show investigates Leonardo’s treatment of the human figure. I was delighted to discover a modest stretch of five drawings of women which actually offers a genuine and profound insight into, yes, the Mona Lisa. The drawings aren’t of her. There are no known preparatory drawings for the Mona Lisa. What we have instead are a St Anne, a Madonna and some Ledas, arranged in a line to reveal and stress their similarities. Every one has playing about her lips that notorious and instantly recognisable smile. The point, excellently and unarguably made, is that all Leonardo’s women sport the same expression. There’s no mystery here. It’s a tactic. Leonardo produced not one Mona Lisa, but scores of them.

This is a sensitive and fastidious exhibition, so the gentle ribbing that’s directed here at the Mona Lisa’s spurious fame is not being done to undermine or accuse either her or Leonardo. It’s neither of their faults that the museum world’s longest-lasting media frenzy continues to swirl around both of them. This show, to its great credit, seems determined to present Leonardo as a practical studio artist rather than the tortured genius. There’s a fabulous sense of the man at work, sifting sensibly through his options, attempting methodically to settle on a final view of the human figure.

His first act is to draw the perfect male, as prescribed by the Greeks. But the ancient proportions he’s been given don’t seem to correlate with the corpses he’s dissecting. So he beavers away in the morgue, observing skeletons and muscle structures with extraordinary visual fierceness. Gluttons eat in the way Leonardo looks. But what I really like about this show is the lack of melodrama it projects onto this behaviour. There’s nothing lurid or horrific or transgressive about the visits to the dissecting rooms. An attempt is being made to see the human figure as it is. That’s all.

The show is called The Divine and the Grotesque, and while most of it investigates Leonardo’s search for a perfect human form, the rest, entertainingly, delves into his world of distortion. This is where the leering old men with hooked noses appear, and the ugly fishwives with distended, John Major-style upper lips. Before he was famous as a scientific genius or as the painter of the Mona Lisa — before he achieved his modern fame — Leonardo was known chiefly for his grotesques. They circled around the studios of Europe and made his reputation.

It’s incredibly difficult to resist the temptation to assume that these hideous girners were intended as a satirical comment upon society and reveal Leonardo’s essential misanthropy. But resist we must. The show announces and proves that Leonardo’s search for “perfect ugliness” was motivated by the same rational urges as his search for perfect beauty. He just wanted to get it right. It says more about us than it does about him that this modest insight feels like a revelation.